Before Chiheb Esseghaier became one of two suspects in a plot to bomb a VIA Rail passenger train, the doctoral student was known to the tenants in a Montreal apartment building as a neighbour from hell, according to a report by La Presse.

“He would scream like a maniac at all hours,” remembered a man identified only as Michel, who lived in the same 20-unit Rosemont complex. “Near the end, I couldn’t take it anymore.”

Departmental officials have been told to look into the files of Chiheb Esseghaier and Raed Jaser, who were arrested Monday on multiple terrorism-related charges, to see whether they pointed to the need for changes in immigration policy.

The minister said Friday he was “disturbed” to learn that Mr. Jaser, a failed refugee claimant, had been able to obtain permanent residence after securing pardons for his crimes. Mr. Kenney said he was also examining why Mr. Jaser had not been deported.

Mr. Jaser, 35, is a Palestinian who flew to Toronto in 1993 using a false passport. Despite convictions for fraud and uttering threats, and despite being rejected as a refugee, Mr. Jaser became a landed immigrant last year after he was pardoned for his crimes.

“That raises for me an important policy question,” Mr. Kenney told reporters. “Why should a pardon override criminal inadmissibility? That’s what I’m looking at with my officials, is to see whether we can make a policy change.’’

Mr. Esseghaier, 30, also obtained permanent residence recently through a Quebec skilled worker program. A Tunisian, he initially came to Canada in 2008 on a student visa and was working on his doctorate in Montreal.

Both men have been charged over what the RCMP has described as an al-Qaeda-linked plot to derail a passenger train traveling from New York to Toronto. As foreign nationals, they could be removed from Canada if convicted.

The policy review was ordered after the National Post reported on the immigration histories of the suspects, notably a 2004 attempt to deport Mr. Jaser that failed because authorities did not know where to send him.

Although Mr. Jaser was born in Abu Dhabi, United Arab Emirates, Canada deemed him “stateless,” meaning without citizenship. The government therefore did not deport him, concluding there was nowhere he could go.

But Mr. Kenney said he would be meeting in the afternoon with officials to “see if there was any way to work to still remove someone like this who allegedly is stateless.” He said he wanted to examine whether someone like Mr. Jaser could be deported to the Palestinian territories.

“I’m looking at all aspects of this case to see if we can learn whether anything more could have been done. But I can certainly tell you that I cannot tolerate that serious criminals would be allowed to stay in Canada in perpetuity based on some pardon.”

The charges refer to an alleged conspiracy to murder train passengers near Toronto between April and September, 2012. The plot is believed to be linked to an al-Qaeda member operating in Iran who provided what police described as “direction and guidance.”

The FBI is holding a third man in New York City but no charges have been formally announced.